Feed displacement correction in a space fed lens antenna

Abstract

A space fed microwave lens antenna for deployment in outer space or other remote, hazardous or unattended location. Electronic means are provided for compensating for errors in the mechanical displacement of the phased array feed elements from the phased array lens elements.

What is claimed is: 
     
       1. Apparatus for electronically correcting the far field pattern of a mechanically misaligned space fed lens antenna comprising: a space fed lens antenna having a phased array feed and a phased array lens;   said phased array feed having a plurality of serially-connected phase shifters and feed elements;   said phased array lens having a plurality of serially-connected phase shifters and lens elements;   range finder means for determining the actual physical displacement of said phased array feed elements from said phased array lens elements and for providing range signals indicative thereof;   controller means for receiving said range signals and for providing first and second phase correction signals functionally related to said actual displacement and desired displacement of said feed elements from said lens elements;   means for applying said first phase correction signals to said phase shifters of said feed elements; and   means for applying said second phase correction signals to the phase shifters of said lens elements;   whereby the far field pattern of said space fed lens antenna is optimized.   
     
     
       2. Apparatus as defined in claim 1 wherein said first phase correction signals vary in accordance with the equation: ##EQU7## where: b n  =amplitude of the signals at the lens elements ##EQU8##  where: (Xf m , Yf m ) are the feed element location coordinates (Xl n , Yl n ) are the lens element location coordinates.   
     
     
       3. Apparatus as defined in claim 2 wherein said second phase correction signals vary in accordance with the equation: ##EQU9## where: A m  *=complex conjugate of the signal at feed element m ##EQU10##  where: (Xf m , Yf m ) are the feed element location coordinates (Xl n , Yl n ) are the lens element location coordinates.   
     
     
       4. Apparatus as defined in claim 3 wherein said controller means further provides amplitude correction signals functionally related to said actual and desired displacement of said feed elements from said lens elements. 
     
     
       5. Apparatus as defined in claim 4 and further comprising: feed signal amplitude adjusters coupled to said phase shifters of each of said feed elements; and   means for coupling said amplitude correction signals to said feed signal amplitude adjusters.   
     
     
       6. Apparatus as defined in claim 5 wherein said amplitude correction signals vary in accordance with the equation: ##EQU11## where: ##EQU12## 
     
     
       7. A method for electronically compensating for undesired variations in the far field pattern of a space fed lens antenna resulting from the misalignment of its phased array feed elements with its phased array lens elements comprising: (a) measuring the actual physical displacement of said feed element from said lens elements and forming range signals indicative thereof;   (b) calculating from said range signals and from predetermined range data related to the proper physical displacement of said feed elements from said lens elements, first and second error correction signals;   (c) applying said first error correction signals to said feed elements to shift the phase of signals therein and thereby lower the sidelobe amplitude taper of said antenna; and   (d) applying said second error correction signals to said lens elements to shift the phase of signals therein and collimate the beam leaving said antenna.